Position sensors are commonly used as input devices for computers, personal digital assistants (PDAs), media players, video game players, consumer electronics, wireless phones, payphones, point-of-sale terminals, automatic teller machines, kiosks and the like. One common type of sensor used in such applications is the touchpad sensor, which can be readily found, for example, as an input device on many notebook-type computers. A user generally operates the sensor by moving a finger, stylus or other stimulus near a sensing region of the sensor. The stimulus creates a capacitive, inductive or other electrical effect upon a carrier signal applied to the sensing region that can be detected and correlated to the position or proximity of the stimulus with respect to the sensing region. This positional information can in turn be used to move a cursor or other indicator on a display screen, scroll through text elements on the screen, or for any other user interface purpose. One example of a touchpad-type position sensor that is based on capacitive sensing technologies is described in U.S. Pat. No. 5,880,411, which issued to Gillespie et al. on Mar. 9, 1999.
While touchpad-type sensors have been in use for several years, engineers continue to seek design alternatives that reduce costs and/or improve sensor performance. In particular, significant attention has been paid in recent years to reducing the effects of noise generated by display screens, power sources, radio frequency interference and/or other sources outside of the sensor. Numerous sampling, filtering, signal processing, shielding, and other noise-reduction techniques have been implemented with varying levels of success.
Accordingly, it is desirable to provide systems and methods for quickly, effectively and efficiently detecting a position-based attribute of an object in the presence of noise. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.